Flutter Spectral Measurements Using Stationary Pressure Transducers

Engine-order sampling was used to eliminate the integral harmonics from the flutter spectra corresponding to a case-mounted static pressure transducer. From the optical displacement data it was demonstrated that blade-order sampling of pressure data can yield erroneous results because of the interference caused by blade vibration. Two methods are presented that effectively eliminate this interference and yield the blade-pressure-difference spectra. The phase difference between the differential-pressure and displacement spectra was evaluated.